1. Field of the Invention
This invention relates to machine tools for processing discrete workpieces and, more particularly, to a machine tool through which individual workpieces can be strategically situated to facilitate processing on various sides thereof. The invention is also directed to a method of using the machine tool.
2. Background Art
In machining operations, it may be necessary to process most or all of the sides of a workpiece. In one conventional machining process, a first surface of a workpiece preform, nominally matched and dimensioned to the desired end configuration, is placed on a support to facilitate processing of the remaining surfaces thereon. Once processing of the remaining surfaces is completed, the first surface is separated from the support and exposed to allow the desired processing step(s) to be performed thereon.
Typically, a three-axis machine tool is employed to carry out the initial stage processing. Provision must then be made to engage and separate the workpiece from the support to expose the first surface to allow processing thereof.
In FIG. 1 herein, a conventional prior art vertical machining center is shown at 10. The machining center 10 consists of a frame 12 on which a spindle head assembly 14 is mounted for guided vertical, Z-axis movement. The spindle head assembly 14 carries a rotary spindle 16 with a working tool 18 that processes discrete workpiece preforms 20, which are mounted in a predetermined relationship on a pallet 22.
The pallet 22 is in turn supported upon a table 24, which is carried upon a slide assembly 25 consisting of stacked slides 26, 28. The lower slide 28 is mounted for guided movement relative to the frame 12 along the Y-axis. The upper slide 26, to which the table 24 attaches, is mounted for guided movement relative to the lower slide 28 along the X-axis.
In a typical machining operation, the workpiece preforms 20 are placed on the pallet 22 so that a surface 30 on each of the workpiece preforms 20 bears upon a support surface 32 on the pallet 22. Through controlled movement of the slides 26, 28, the workpiece preforms 20 are moved in the X-Y plane. At the same time, the working tool 18 moves along the Z-axis, following movement of the spindle head assembly 14.
The workpiece preforms 20 are spaced from each other so that all but the supporting surfaces 30 are exposed to be processed by the working tool 18. After the processing operation is concluded on the exposed portions of the workpiece preforms 20, the workpiece preforms 20 are separated from the pallet 22 and reoriented, as by inversion, and placed against the palle surface 32 to expose the surfaces 30 so that an appropriate processing operation can be performed using the working tool 18, or another tool in its stead.
The resituation of the workpiece preforms 20, during processing thereof, may result in significant down time.
Further, it is common for the workpiece preforms 20 to be manually placed upon the pallet 22, and for the workpiece preforms 20, after processing, to be manually separated from the pallet 22. This may result in significant inconvenience and time consumption.
Alternatively, it is known to use relatively complex and expensive automated setup systems with changers for removing an inactive table 24/pallet 22 and substituting therefor a table 24/pallet 22 with unprocessed workpiece preforms 20 thereon. The table 24/pallet 22 exchange may take a significant amount of time. Also, a significant time investment may be involved by reason of the manual placement and removal of workpiece preforms 20 both prior to and after the performance of a machining operation.
The invention is directed to a method of processing a workpiece including the steps of: placing a first preform element in a first operative position on a first holder so that a first portion of the first preform element is exposed; performing a processing operation on the first portion of the first preform element with the first preform element in the first operative position; transferring the first preform element into a second operative position on a second holder; with the first preform element in the second operative position exposing a second portion of the first preform element that is not exposed for processing with the first preform element in the first operative position; and with the first preform element in the second operative position and the second portion of the first preform exposed, performing a processing operation on the second portion of the first preform element.
The second portion of the first preform element may be exposed by cutting the first preform element.
A single processing assembly may be used to perform the processing operations on both the first and second portions of the first preform element. Alternatively, a first processing assembly may be used to perform the processing operation on the first portion of the first preform element with a second processing assembly, operable independently of the first processing assembly, used to perform a processing operation on the second portion of the first preform element.
A second preform element can be placed in the first operative position on the first holder with the first preform element in the second operative position on the second holder.
A processing operation may be performed on the second preform element in the first operative position on the first holder with the first processing assembly while performing a processing operation on the first preform element in the second operative position on the second holder with the second processing assembly.
A second preform element can be provided on the first holder so that the first and second preform elements are simultaneously held by the first holder. After the step of performing a processing operation on the first portion of the first preform element by the first processing assembly, the first processing assembly and the second preform element may be relatively repositioned to allow the first processing assembly to perform a processing operation on the second preform element with the second preform element on the first holder.
The first processing assembly may have a first processing tool thereon. During the processing operation on the first portion of the first preform element, the processing tool may be moved along at least two orthogonal axes.
The second processing assembly may have a plurality of tools that are selectively indexed to an active position in which each of the plurality of tools in the active position performs a processing operation on the second portion of the first preform element.
The first preform element may be indexed on the first holder between a standby position and the first operative position.
The first preform element may be transferred directly from the first holder to the second holder.
The invention is also directed to a machine tool having a first holder, a second holder, and a processing system. The first holder maintains a first preform element in a first operative position wherein a first portion of the first preform element is exposed so that a machining operation can be performed on the first portion of the first preform element. The second holder maintains the first preform element in a second operative position wherein a second portion of the first preform element that is not exposed for processing with the first preform element in the first operative position is exposed for processing. The processing system has at least one processing assembly for performing a processing operation on the first portion of the first preform element in the first operative position and the second portion of the first preform element in the second operative position.
At least part of the at least one of the first and second holders may be movable guidingly relative to the other of the first and second holders to allow the first preform element to be transferred directly from the first holder to the second holder.
In one form, the at least one processing assembly is a first processing assembly that is repositionable relative to the first and second holders to allow the first processing assembly to perform a processing operation on the first preform element in the first operative position and a processing operation on the first preform element in the second operative position.
In one form, the first processing assembly has a first tool that is rotatable around a first axis for performing a processing operation and at least one part of the first processing assembly carrying the first tool is pivotable around a second axis that is transverse to the first axis to permit selective processing of the first preform element in the first and second operative positions for the first preform element.
The machine tool may be provided in combination with a first preform element.
The processing system may include a second processing assembly that is operable independently of the first processing assembly to perform a processing operation on the first preform element in the second operative position.
In one form, a cutting assembly, separate from the first and second processing assemblies, is provided for severing the first preform element on at least one of the first and second holders and thereby exposing the second portion of the first preform element.
The second processing assembly may include a turret with a plurality of tools that are selectively operable to perform a processing operation on the first preform element in the second operative position.
The first holder may be capable of holding a second preform element at the same time the first preform element is on the first holder.
The second holder may be capable of holding a second preform element at the same time the first preform element is on the second holder.
The first and second preform elements on the first holder may be selectively movable into the first operative position.
The first and second preform elements on the second holder may be selectively movable into the second operative position.
In one form, the at least part of the first processing assembly is movable guidingly along three orthogonal axes.
The turret may be translatable guidingly along two orthogonal axes.
The first processing assembly may include a tool receptacle, with the machine tool further having an automatic tool changer for selectively placing different tools in the tool receptacle.
A frame may be provided upon which the first and second holders and processing system are mounted.